Mahoney first began performing as a member of a children's theater, the database said. After graduating high school, Mahoney immigrated to America, and joined the US Army at age 19, according to Studio System, a TV and film database.

Mahoney earned a bachelor of arts from then-Quincy College in Quincy, Illinois, and a master of arts from Western Illinois University in Macomb, Illinois, according to Studio System.

He worked as a college professor and a medical orderly and later edited a hospital periodical, according to Studio System.

In his 30s, he enrolled in acting classes at Chicago's St. Nicholas Theatre after quitting his job. In 1977, Mahoney made his professional stage debut in "The Water Engine" in Chicago age the age of 37, Studio System said.